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Psychology 150 Psychology 150 Introduction to PsychologyIntroduction to Psychology

Lecture 09 - 09/19/01• Finishing Perception – 2D 3D• Attention?

Sample Problem:Sample Problem:Depth PerceptionDepth Perception

Retina is a 2-D surface - How do you perceive depth?

Two types of cues…

Binocular CuesBinocular Cues

Binocular Disparity.

Binocular CuesBinocular Cues

Binocular Disparity.– The less the disparity, the greater the

distance.– Sufficient for Depth Perception (stereopsis)

Eye Convergence

Monocular Cues to DepthMonocular Cues to Depth

Motion Parallax

Monocular Cues to DepthMonocular Cues to Depth

Motion ParallaxOcclusion

Monocular Cues to DepthMonocular Cues to Depth

Motion ParallaxOcclusionRelative Image Size

Monocular Cues to DepthMonocular Cues to Depth

Motion ParallaxOcclusionRelative Image SizeTexture Gradients & Linear Perspective

Monocular Cues to DepthMonocular Cues to Depth

Motion ParallaxOcclusionRelative Image SizeLinear PerspectiveTexture GradientsPosition Relative to Horizon

Problem: Problem: Perceptual ConstancyPerceptual Constancy

Our perception that properties of objects remain constant even when the conditions of stimulation are changed.

Example: Color Constancy– Is color perception solely a function of

wavelength?

Top-Down Effect on Early Top-Down Effect on Early Perceptual ProcessingPerceptual Processing

Steven Palmer (1975)Theory:

Even Early Perceptual Processes are dependent upon the current cognitive state of the perceiver...

Palmer’s ExperimentPalmer’s Experiment

Subjects: HumansTask: Look at Object 1, and then identify

a briefly flashed object (Object 2)

Palmer’s ExperimentPalmer’s Experiment

Manipulation: Conceptual Relationship between Object 1 and Object 2 (consistent or inconsistent).

Palmer cont...Palmer cont...

Measure: Percent Correct IdentificationPrediction: Consistent relationship

between object 1 and object 2 will increase perceptual identification.

Results...

Palmer, 1975

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Consistent Inconsistent

Relationship between Objects

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Summing Up PerceptionSumming Up PerceptionGoal: Stable representation of reality.Problem: Need to transduce “incomplete”

incoming stimulus energy and “construct” a percept.

Not a one-to-one relationship between stimulus and perception.

Behavioral study can guide neuroscience.Construction Project = Unconscious

Inference.

Pay Attention:

Dropping Rocks and Frog Legs Ahead!

&$%#* Brain Again&$%#* Brain Again

Nice device and all, but… – Finite!– Distracting Stimuli.

Attention: A mechanism for selection.Attention is a hypothetical construct.

Dropping RocksDropping Rocks

How do you demonstrate the properties of gravity?

We need a dropping rock for cognition!

Frog LegsFrog Legs

Helmholtz - Does nerve conduction take time?

If nerve conduction takes time….Reaction Time: The elapsed time between

the onset of a stimulus and the subject’s response.

An example that puzzled me…An example that puzzled me…

Behavior Boy… takes a cognitive course...

Background:Background:Basic Detection ParadigmBasic Detection Paradigm

Time 1 Time 2

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Sample Data for Visual Detection Task

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